The present invention relates to new polyarylalkane oligomer compositions, a process for their manufacture, and products utilizing such compositions.
These products can be used as a microencapsulation solvent for rupturable microcapsules used to make carbonless transfer paper and for other products for which microcapsules can be used.
In Patent EP No. 136,230, the person skilled in the art has already proposed mixtures of oligomers based on benzyltoluene, dibenzyltoluene and ditolylphenylmethane, which exhibit the advantage, when compared with these same oligomers taken separately, of crystallizing at very low temperature and of having a viscosity which is always compatible with their application as a dielectric for capacitors. These characteristics make them most particularly suitable for use as a microencapsulation solvent for microcapsules for such uses as in making carbonless transfer paper. However, they have a characteristic which disqualifies them for such use; namely, a highly unpleasant odor which is disclosed just like the color when the microcapsules are ruptured, at the time of hitting the keys of a typewriter, for example. The compositions according to the invention not only have a viscosity which is compatible with the application, but are also characterized by an "absence of odor" which is absolutely essential in the intended application as a microencapsulation solvent for forming microcapsules.
Patent GB No. 1,346,364 summarizes the properties which must be reconciled in microencapsulation solvents:
(i) dissolving the dye, (ii) not evaporating when the microcapsules are processed, (iii) being inert towards the encapsulation material, (iv) not reacting with the solvent developer,
(v) having a viscosity which is low and relatively insensitive to temperature, and (vi) not having an unpleasant odor.
Since the disadvantages of mono- and dibenzylalkylbenzenes have also long been known, many substitute mixtures have been proposed, starting with polyarylalkane oligomers. However, it is always difficult to reconcile the quality of the properties of the products obtained with the economic aspect of the means for producing this substitute product.
Thus, Japanese Patent Application JP-Kokai No. 73-86,612 describes the use of di(propylbenzyl)propylbenzene, the synthesis of which calls for a large number of reaction and separation stages due to the nonselectivity of a synthesis of this type.
Lastly, in Japanese Patent Application JP-Kokai No. 78-42,909 reference is made to the use, as a microencapsulation solvent, of the following isomers:
(i) ditolylphenylmethane,
(ii) tolyldiphenylmethane, and
(iii) tritolylphenylmethane.
The synthesis of each of these isomers calls for specific reactions, for example tolyldiphenylmethane from benzylidene chloride, toluene and benzene, followed by a separation of the isomers. Moreover, a mixture of these products must then be produced, and this is hardly advantageous from the standpoint of economy.
As a general rule, the prior art shows products for the microencapsulation solvent application of the monobenzylalkylbenzene or dibenzylalkylbenzene or, alternatively, di(alkylphenyl)phenylmethane type, but which can be manufactured only using relatively nonselective syntheses.